The present invention relates to a liquid crystal display panel used in a display or the like of a computer, and more particularly, to a thinner display panel.
FIG. 14 is a basic configuration view of a conventional liquid crystal panel unit of a back light type described in, for example, page 337 of an additional edition of a monthly Semiconductor World "'95 Latest Liquid Crystal Process Art". Referring to the drawing, numeral 1 is a polarizer and numeral 2 is a liquid crystal panel composed of a color filter 3 and an array substrate 4. Numeral 5 is a driving circuit for image displaying connected with the array substrate 4. A back light comprises a diffusion sheet 6 for scattering and equalizing light, a light guide plate 7, a reflective sheet 8 placed on the reverse side of the light guide plate 7, a cold cathode tube (lamp) 9, and a reflective plate 10. Numeral 30 is an inverter for providing AC power of high voltage to the lamp 9.
FIG. 15 is a sectional view showing a comparative embodiment for explaining effects of the present invention. In FIG. 15, numeral 1 is a polarizer (thickness: 0.21 mm), and numeral 2 is a liquid crystal panel composed of a color filter 3 (thickness: 0.5 mm) and an array substrate 4 (thickness: 0.4 mm). Numeral 6 is a diffusion sheet (thickness: 0.14 mm); numeral 7 a light guide plate (thickness: 2 mm); numeral 8 a reflective sheet (thickness: 0.125 mm); numeral 9 a lamp (diameter: 2 mm); and numeral 10 an Ag reflective plate (thickness: 0.05 mm), respectively. Further, numeral 11 is an insulating film (thickness: 0.1 mm); numeral 12 a back metal plate (thickness: 3 mm) of a metal housing; numeral 13 a metal housing frame; numeral 14 a front metal plate (thickness: 3 mm) of the housing; numeral 15 a decorative sheet (thickness: 0.2 mm); numeral 16 two prism sheets each having a thickness of 0.16 mm; and numeral 17 a bonding material (thickness: 0.1 mm) respectively. Further, numerals 34 to 36 are a groove for allowing a low voltage wiring of the lamp to pass, plastic mold and a frame coated with black ink for preventing directly reflected light from the lamp from being observed, respectively. In FIG. 15, sizes of t11 to t15 and t17 to t22 are 0.5 mm (t11), 3.795 mm (t12), 0.3 mm (t13), 0.4 mm (t14), 0.2 mm (t5), 0.5 mm (t17), 3.995 mm (t18), 0.3 mm (t19), 1.62 mm (t20), 2 mm (t21) and 0.375 mm (t22: 0.1 mm of bonding material +0.125 mm of reflective sheet +0.05 mm of Ag sheet +0.1 mm of insulating film), respectively.
The operation of the panel unit will be described. A DC power of approximately 5 through 12 V to be provided from a battery is converted into an AC power of 40 through 200 kHz in frequency, and approximately 500 through 1500 V in effective voltage by the inverter 30 and is applied to the high voltage terminal of the lamp 9. The other end is earthed to allow the lamp 9 to emit light with potential distribution shown in FIG. 5. The light emitted from the lamp 9 enters into the light guide plate 7 and spreads on the whole face of the light guide plate 7 while being reflected by the reflective sheet 8. At this time, the periphery of the lamp 9 is surrounded by a reflective plate 10 so as to let more light enter into the light guide plate 7 without waste. In order to raise the reflectance, a sheet with silver being spattered on it is used as a reflective plate 10. Thus, a capacity coupling is formed among the lamp 9, silver reflective plate 10, and a housing metal portion adjacent thereto, and a leak pass of the high frequency power applied to the cold cathode tube is formed. The scattered dots are formed on the reverse face of the light guide plate 7. The light scattered at the reverse face of the light guide plate 7 and coming from the front face of the light guide plate 7 is scattered by the diffusion sheet 6 to be equalized. Furthermore, the light enters into a liquid crystal after the light have been throttled in a direction vertical to a panel face by a prism sheet. In the liquid crystal panel, after the incident light has been polarized by the polarizer 1, the polarization direction of the light is rotationally shifted for each dot in accordance with the image signal at the liquid crystal panel 2 to which the voltage has been applied with the driving circuit 5, and the light passes through a color filter. Finally, only the light rotated by 90 degrees in the polarization direction by a second polarization plate 1 which is an analyzer, can be transmitted.
In order to form a thin type liquid crystal display panel including an external panel, the liquid crystal display of a back light type has the following problems simultaneously with a problem of thinning.
(1) measures against electromagnetic injuries (EMI) PA1 (2) reduction of consumption power (2 W or lower) PA1 (3) impact resistance (not broken with impact of 200 G)
Accordingly, an object of the present invention is, in a panel module using a metal housing with a large impact resistance which becomes a stable ground and has an electromagnetic shielding function, to restrain increase of leakage current due to thinning from between a back light lamp and a panel housing to improve the equalization of lamp radiation, thereby reducing the load of a high frequency current supply circuit.